If young people are born 'peaceful'—without prejudiced or militaristic attitudes—why must they also be meticulously taught it through 'peace education' programs? Combining historical archival research from five U.S. governmental, university, and other English-language libraries along with critical discourse analysis, this dissertation makes interventions in three fields: Peace Studies, Critical Youth Studies, and the historical sub-field of the "U.S. in the World." This dissertation surveys how American social scientists, especially social psychologists, produced knowledge about the nature of 'child development' as well as 'intergroup contact' from the interwar period through the early Cold War years. It also considers how these theories influenced the design of the most popular private and governmental 'people-to-people' peace education programs. Finally, this dissertation examines why U.S. government officials and policymakers came to believe that these programs were useful to the expansion of U.S. power in the world during and after the Second World War and into the early Cold War period.This dissertation demonstrates that these various people-to-people programs of the past rarely produced the desired results. Policymakers found that people-to-people exchanges did not automatically influence foreign audiences to want to follow the, purported, American way of 'democratic living' or to accept U.S. foreign policy objectives. However, they did help solidify a dominant theory of change undergirding the design of mainstream American people-to-people programs. These liberal programs tended to favor a combination of education about select 'other' groups of people and, increasingly, mediated interpersonal contact with these 'other' groups. Consequently, changing individual attitudes, via interpersonal contact, was emphasized over other possible structural changes, such as addressing discriminatory practices and institutions. Over time, these programs also came to target 'youth' as a distinct category of persons assumed to be most suitable for these programs. In being named the ideal 'ambassadors of peace' and the best participants for various people-to-people programs, a category of persons named 'youth' was, in effect, transformed into the recipients most in need of an education for 'peace'.